Is there a way to control sleep / power settings in a Windows Server 2003 AD via GPO? Ideally, without installing anything on the client, or running scripts on the client?
Ultimately I am looking to find the 'hybrid sleep' setting for Windows 7 if possible and turn that off.
Energy Star has a number of aticles on using GPO to control paower settings. One for WIN7 /Vista is here EnergyStar  http://www.energystar.gov/index.cfm?c=power_mgt.pr_power_mgt_enterprises_winVista
Windows 7 has a bug where the power options for Hybrid sleep actually do the opposite of what they are supposed to do. This is resolved with a hotfix. If you want to create GPOs that can accommodate either client (fixed or not), you should have a WMI filter that checks for the version of the offending file (gpprefcl.dll) and the service pack version.
Power options do not work correctly in Windows 7 or in Windows Server 2008 R2 when you use Group Policy to configure the power plan in a domain
When you use Group Policy to configure the power plan in a domain, power options do not work correctly on a client computer that is running Windows 7 or Windows Server 2008 R2.
For example, you use Group Policy to configure the Allow hybrid sleep setting to OFF. However, you may notice that the Allow hybrid sleep setting is set to ON instead of to OFF on a client computer that is running Windows 7.
This issue occurs because the index value setting in Group Policy is the opposite of the index value setting in Windows Power Management.
These settings are controllable via group policy preferences under the Computer->Group Policy Preferences->Control Panel->Power (or similar) settings.